I think this can be done with cron jobs but how exactly? I don’t use cron jobs much so I need detailed help.
How many people will you be sending to? It might be worth it looking at a paid service like Mailchimp or Amazon SES.
Building a mail service for a lot of emails is one of the hardest things to do and 9 of 10 times getting a paid service is cheaper in the long run because you don’t have to worry about all the maintenance stuff like blacklisting etc.
Yes you can do that as well, but the same limitation holds. You can probably go faster than 1 every minute, but google apps also doesn’t like it if you blast a lot of emails at it. No SMTP server does. Which is why I suggested the alternatives
What I did is echoed out all the usernames and emails from my table to a file then used MaxBulk Mailer and connected to my google apps account. Then I loaded the emails from web page and boom they all popped up which then allowed me to create a nice message and send to all users.